An improved furlable antenna particularly suited for use in a celestial space environment is described. The antenna is characterized by an actuator comprising an elastomeric member of an annular configuration, an annular array of uniformly spaced antenna ribs rigidly affixed at the base ends to an actuator which enables it to be supported for pivotal displacement from a deployed configuration. The ribs are radially extended from the actuator to a furled configuration. The ribs are extended parallel to the axis of the actuator with flexible reflecting web affixed to the ribs, with angularly spaced bearing blocks

Barnett, M. A.

English

NASA Technical Reports Server

[I91 [ 1 11  3,978,490 
Fletcher et al. [451 Aug. 38, 119’76 
[541 FURLABLE ANTENNA 
[76] Inventors: James C. Fletcher, Administrator of 
the National Aeronautics and Space 
Administration, with respect to an 
invention of; Morris A. Barnett, 
South Pasadena, Calif. 
[ 2 2 ]  Filed: Sept. 24, 1975 
[ 2 1 ] Appl. No.: 616,333 
[ 5 2 ]  
[ 5  I ]  
[ 5 8 ]  
U.S. C1. ................................. 343/882; 343/915 
Int. CI.* ......................................... HOlQ 15/20 
Field of Search ............ 343/840, 881, 882, 915 
[561 References Cited 
UNITED STATES PATENTS 
3,671,965 611972 Rabenhorst et  al ................. 3431915 
3,680,144 511972 Ludwig ............................... 3431840 
Primary Examiner-Eli Lieberman 
Attorney, Agent, or Firm-Monte F. Mott; Wilfred 
Grifka; John R. Manning 
[571 ABSTRACT 
An improved furlable antenna particularly suited for 
use in a celestial space environment. The antenna is 
characterized by an actuator comprising an elasto- 
meric member of an annular configuration, an annular 
array of uniformly spaced antenna ribs rigidly affixed 
at the base ends thereof to said actuator and sup- 
ported thereby for pivotal displacement from a de- 
ployed configuration, wherein the ribs are substan- 
tially radially extended from said actuator to a furled 
configuration wherein the ribs are extended in sub- 
stantial parallelism with the axis of the actuator, a 
flexible reflecting web affixed to the ribs, and a plural- 
ity of angularly spaced bearing blocks supporting 
every radially extended section of the member for ro- 
tation about its own centroid. 
6 Claims, 7 Drawing Figures 
I4 
https://ntrs.nasa.gov/search.jsp?R=19760025369 2020-03-20T02:23:49+00:00Z
U.S. h k n &  Aug. 31, 1976 Sheet 1 of 2 3,978,490 
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U.S. Patent Aug. 31, 19-76 Sheet 2 of 2 3,978,490 
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3,978,490 
1 
FURLABLE ANTENNA 
ORIGIN OF THE INVENTION 
The invention described herein was made in the per- 5 
formance of work under a NASA contract and is sub- 
ject to the provisions of Section 305 of the National 
Aeronautics and Space Act of 1958, Public Law 
85-568 (72 Stat. 435; 42 USC 2457). 
BACKGROUND O F  THE INVENTION 
10 
1. Field of the Invention: 
The invention generally relates to  antennas and more 
particularly to an improved furlable antenna having an 
improved actuator for effecting selective deployment 15 
of the antenna reflector. 
Future spacecraft missions to the outer planets of our 
solar system will require communication systems capa- 
ble of transmitting data at significantly expanded data 
rates. Expanded data rates, in turn, require a use of 20 
antennas having reflectors of increased dimensions. 
Because of weight and bulk limitations imposed by the 
designers of space vehicles, antenna reflectors having 
an operating diameter larger than the dimensions of 
spaces provided for stowage, must be so constructed as 
to accommodate furling in order to facilitate stowage, 
and unfurling in order to achieve deployment. 
2. Description of the Prior Art: 
As is fully appreciated by those engaged in the design 
and fabrication of communication systems for use 
aboard operating spacecraft, numerous designs for 
antenna reflectors capable of being furled and unfurled 
have been proposed. In most instances it has been as- 
sumed by the designer of the furlable reflector that 
some suitable actuator for unfurling or  deploying the 
reflector will be made available by others. Yet, as 
should be apparent, a satisfactory actuator should be of 
light weight and reliable construction, simple to oper- 
ate and economic to fabricate. As a consequence of 
this combination of requirements, there exists a dearth 
of suitable antennas having capabilities necessary for 
assuring completion of successful missions. 
It is, therefore, the general purpose of the instant 
invention to provide for use in a communication sys- 
tem, particularly adapted for use in celestial space, an 
improved antenna having a reflector of increased di- 
mensions, for accommodating expansion of data rates 
and equipped with a simple, economic, lightweight and 
reliable actuator and having a capability for being 
launched aboard existing spacecraft in a furled configu- 
ration and subsequently expanded into an unfurled 
deployed configuration. 
OBJECTS AND SUMMARY OF THE INVENTION 
It is, therefore, an object of the instant invention to 
provide an improved antenna which overcomes the 
aforementioned difficulties and disadvantages. 
It is another object to provide an antenna particularly 
suited for use in a celestial space environment having 
an improved reflector characterized by increased di- 
mensions for accommodating expanded data rates. 
Another object is to provide a furlable antenna hav- 
ing an improved actuator capable of storing energy, as 
the antenna is furled, for subsequent release to effect 
an automatic unfurling of the antenna into a deployed 
configuration. 
Another object is to provide an improved antenna 
characterized by a furlable reflector connected for 
25 
30 
35 
40 
45 
50 
5 5  
60 
65 
2 
deployment with an improved actu?tor conforming 
substantially to an annular member, each radial section 
thereof being supported for rotation in its plane about 
its centroid. 
Another object is to provide in a furlable antenna an 
improved actuator which is particularly useful in de- 
ploying the antenna in celestial space, although not 
necessarily restricted in use thereto since the actuator 
may be similarly useful when installed in devices such 
as clutches and the like, as will more readily become 
apparent by reference to the following description and 
claims in light of the accompanying drawings. 
These and other objects and advantages are achieved 
by coupling with a furlable antenna of the type having 
an annular array of uniformly spaced antenna ribs and 
a flexible reflecting web, a deployment actuator includ- 
ing an annular member formed of elastomeric materi- 
als, characterized by a selected elastic modulus, and 
supported in a manner such that every radially ex- 
tended section of the member is supported for rotation 
in its own plane, about its own centroid, whereby as the 
array is displaced to its furled configuration energy is 
stored in the annular member, preparatory to its being 
released for deploying the antenna. 
BRIEF DESCRIPTION OF THE DRAWINGS 
FIG. 1 is a perspective view of a furlable antenna 
having provided therefor a deployment actuator of an 
annular configuration supporting a plurality of ribs 
upon which is mounted a reflector of flexible material. 
FIG. 2 is a fragmented top plan view of the antenna, 
taken generally along line 2-2 of FIG. 1. 
FIG. 3 is a perspective view illustrating the antenna in 
a furled configuration. 
FIGS. 4 and 5 are fragmented, partially sectioned 
views illustrating alternative structure adapted to be 
employed in connecting the ribs with the actuator. 
FIG. 6 is a perspective view of the actuator illustrat- 
ing laminar construction. 
FIG. 7 is a diagrammatic view illustrating operation 
of the actuator. 
DESCRIPTION OF THE PREFERRED 
EMBODIMENT 
Referring now to the drawings, with more particular- 
ity, wherein like reference characters designate like or  
corresponding parts throughout the several views, 
there is shown in FIG. 1 an improved antenna which 
embodies the principles of the instant invention. 
As shown in the drawings, the antenna includes a 
furlable reflector, generally designated 12, of a dish- 
shaped configuration and formed of a flexible reflector 
material 13. The specific configuration of the reflector 
forms no specific part of the invention and may be 
varied as desired. An elongaged structural support, 
designated 14, is coaxially aligned with said reflector 
and is provided for supporting an electronic receiver- 
transmitter package along the axis of the antenna, in a 
manner fully appreciated by those familiar with the 
principles of antenna design. The structural support 14, 
further, serves as a base upon which is mounted an 
actuator 16, the purpose of which will hereinafter be- 
come apparent. The material 13 preferably is a flexible 
mesh material, which also forms no specific part of the 
instant invention, however, it is to be understood that 
where so desired, the material 13 comprises a metallic 
mesh. 
3,978,490 
3 
To the structural support 14 there is affixed a plural- 
ity of angularly spaced bearing blocks 18 intercon- 
nected through suitable links 20. The links are united in 
an end-to-end relationship to form a triangular truss for 
supporting the bearing blocks in a fixed relationship. 
The links 20 are connected with the bearing blocks 18 
in any suitable manner, such as by welding and the like. 
Each of the bearing blocks 18, in turn, includes a bore 
formed therein within which there is inserted a suitable 
plain bearing sleeve, not shown, which serves to receive 
a segment of the actuator 16. 
The actuator 16 comprises an annular member 
formed of elastomeric material having a suitable elastic 
modulus. Where so desired, the actuator 16 is fabri- 
cated from annular layers of fiberglass, FIG. 6, dis- 
posed in superimposed relation and supported in an 
epoxy matrix, and is of prestressed construction, where 
so desired, in order to establish predetermined torque 
characteristics therefor. 
Attached to the actuator 16 in uniformly spaced 
relation, there is an annular array of ribs 22 which serve 
to support the flexible material 13. The material is 
united with the ribs 22 in a suitable fashion, such as 
through a use of epoxy. 
The base end of each of the ribs 22 is provided with 
an eye 24 through which the actuator 16 is extended. 
The eye is attached to the actuator in any suitable 
manner including, where so desired, a use of pins 26, 
FIG. 4, extended through the actuator 16 or, where so 
desired, the eyes can be characterized by noncircular 
cross-sectional configurations, as best illustrated in 
FIG. 5. In any event, it is to  be understood that the ribs 
22 are rigidly affixed at  their base ends to the annular 
actuator 16 in a manner such that when the antenna is 
deployed the ribs 22 extend substantially radially from 
the annular actuator 16, in uniformly diverging pat- 
terns, as illustrated in FIG. 1. Similarly, when the re- 
flector 12 is in its furled configuration, as illustrated in 
FIG. 3, the ribs 22 extend in substantial parallelism. 
Thus, the ribs 22 are affixed at their base ends to the 
annular actuator 16 and form an annular array of uni- 
formly spaced antenna ribs which serve to support the 
reflector 12 in its furled as well as its deployed or un- 
furled configuration. 
OPERATION 
It is believed that in view of the foregoing descrip- 
tion, the operation of the device will readily be under- 
stood and it will be briefly reviewed at  this point. 
With the antenna assembled in the manner hereinbe- 
fore described, it is to be understood that when the 
annular array of uniformly spaced antenna ribs are in a 
substantially radially extended relationship with the 
annular actuator 16, the flexible material 13 is drawn 
taut and configured in a slightly conical or parabolic 
configuration suitable for use as an  antenna reflector in 
a communication link. Alternatively, when the annular 
array of uniformly spaced antenna ribs 22 are arranged 
in substantial parallelism, as illustrated in FIG. 3, the 
reflector 12 is in its furled configuration, particularly 
suited to  be received by shrouds of a launch vehicle. 
In order to impart to the antenna a furled configura- 
tion, the ribs 22 are simultaneously pivoted into mutual 
parallelism, as illustrated in FIG. 3. As illustrated in 
FIG. 7, the pivoting of the ribs tends to cause the annu- 
lar actuator 16 to rotate, each section about its own 
centroid. Such rotation is accommodated by the bear- 
ing blocks 18 and since the ribs 22 are affixed to the 
annular actuator 16, forcing the ribs into mutual paral- 
lelism tends to roll the annular actuator inwardly, in 
effect, tending to turn the actuator outside in. This 
causes the actuator to undergo bending. It is important 
4 
here to appreciate that energy is thus stored in the 
actuator, even though the actuator is permitted to turn 
outside in, as illustrated in FIG. 7. 
Once a space vehicle, having the antenna stowed 
5 aboard in a furled configuration, is launched, and a 
shroud confining the furled antenna is ejected, the 
antenna is released from confining restraint, where- 
upon the ribs 22 are pivoted outwardly into their sub- 
stantial radial relationship by the actuator 16 for thus 
,o tightening the flexible material 13 in its deployed con- 
figuration. Thus the actuator 16 functions to deploy or 
unfurl the reflector 12 in response to a release of en- 
ergy stored therein as the antenna is reduced to its 
furled configuration. 
In view of the foregoing, it should readily be apparent 
that the antenna of the instant invention provides a 
practical solution to the perplexing problem of reliably 
achieving deployment of relatively large dish-shaped 
antenna reflectors adaptcd to be put into a celestial 
space environment employing space vehicles having 
Although the invention has been herein shown and 
described in what is conceived to be the most practical 
and preferred embodiment, it is recognized that depar- 
tures may be made therefrom within the scope of the 
25 invention, which is not to be limited to the illustrative 
details disclosed. 
20 limited stowage capacities. 
What is claimed is: 
1. A furlable antenna comprising: 
A. a deployment actuator including an  annular mem- 
ber characterized by a selected elastic modulus; 
B. an annular array of uniformly spaced antenna ribs 
rigidly affixed at  one end thereof to said annular 
member and supported by said member for pivotal 
displacement from a deployed configuration, 
wherein the ribs are extended substantially radially 
from said annular member, to a furled configura- 
tion wherein said ribs are extended in substantial 
parallelism; 
C. a flexible reflecting web extended between said 
ribs and affixed thereto; and 
D. a plurality of bearing blocks rotatably supporting 
said annular member in a manner such that every 
radially extended section of the member is sup- 
ported for rotation in its own plane, about its own 
centroid, as said array is displaced. 
2. The antenna of claim 1 wherein said one end of 
45 each of said ribs includes an eye and said member is 
extended therethrough. 
3. The antenna of claim 2 wherein said member in- 
cludes a plurality of uniformly spaced segments of a 
noncircular cross-sectional configuration concentri- 
50 cally related to the eye of each of the ribs of said array. 
4. The antenna of claim 2 further including a plural- 
ity of uniformly spaced pins extended through said 
annular member for connecting said ribs with said an- 
nular member. 
5. The antenna of claim 2 wherein said member in- 
cludes a plurality of annular layers of fiberglass held in 
30 
35 
40 
5 5  
an epoxy matrix. 
ing: 
6. In a furlable antenna, an improved actuator includ- 
A. an annular member having a selected elastic mod- 
ulus comprising a plurality of annular layers of 
fiberglass held in an epoxy matrix; and 
B. means supporting said member including a plural- 
ity of uniformly spaced bearing blocks supporting 
said annular member in a manner such that every 
radially extended section of the member is sup- 
ported for rotation in its own plane, about its own 
centroid. 
6o 
65 
* * * * *  


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